Drill collar stabilizer



May 9, 1967 D. R. OWEN 3,318,398

DRILL COLLAR STABILI ZER Filed June 30, 1964 fla/e 7?. Owen INVENTOR.

W R LM ATTOF/VE VJ United States Patent ()filice 3,318,398 Patented May9, 1967 3,318,398 DRILL COLLAR STABILIZER Dale R. Owen, deceased, 311Claymore Drive, Lafayette,

La. 70501; Ray F. Fry, as tutor of Lauren Owen,

Tracy Owen, and Kelly Owen, minor children of said Dale Owen Filed June30, 1964, Ser. No. 379,100 12 Claims. (Cl. 175-323) The inventionconcerns a stabilizer suitable for con nection and use in a drillstring, particularly for connection to one or more drill collars in adrill string.

Stabilizers are frequently employed during the drilling of wells tocenter the drill collars in the well bore and provide better alignmentin the hole being drilled. The stabilizers usually comprise a tubularbody having means at each end for connection in the drill string and aplurality of blades or rollers disposed circumferentially on theexternal surface of the tubular body. The blades or rollers usuallyextend from the tubular body for a distance sufficient to permitstabilization in the Well bore, for example, for a distance such thatthe diameter of the outside circumference of the blades or rollers isabout equal to or slightly less than the diameter of the well bore orthe outside diameter of the drill bit.

Stabilizers when suitably placed in a string of drill collars can keepthe collars centered in the hole and minimize sidewise drilling of thebit, thereby helping to effect a substantially straight hole.Stabilizers can also help to prevent sticking of the drill collars inthe well bore since the stabilizers keep the surfaces of the collarsaway from the wall of the well bore. Stabilizers are also useful whenplaced a suitable distance from the drill bit to straighten a slantingwell bore more towards vertical because of the pendulum effect achievedwhen the weight of drill collars below the stabilizer is rather large.

The invention provides a novel stabilizer construction which in variousembodiments exhibits improved characteristics over the stabilizers knownheretofore. One embodiment exemplifying the invention comprises atubular body; means at each end of the body for permitting connection ina drill string; at least two substantially helical bars or bladesfixedly mounted on and circumferentially spaced around the externalsurface of the body; and at least one ridge substantially longitudinallydisposed on the external surface of the body between each adjacent pairof the bars near the ends of the bars which trail during entry into awell bore, this ridge minimizing circumferential erosion of the body bydrilling fluid around the tubular body immediately above the trailingends of the bars during entry into the well bore.

Preferably the stabilizer defined above has ridges made of hard metalwhich extend longitudinally of the body from a point below the trailingends of the bars to a point above the trailing ends of the bars for adistance sufficient to minimize circumferential erosion of the body by adrilling fluid. Since commercial stabilizers are usually between about 3feet and above 5 feet long depending on the size of the well bore andthe size of the drill collar with which the stabilizer is to beassociated and the helical bars or blades are between about inches andabout 20 inches long ordinarily a ridge :between about 3 inches and 6inches long will minimize circumferential erosion sufficiently.Likewise, for most commercially known uses the ridge may be up to about/2 inch wide and up to about /2 inch high a ridge of about 41 to about Ainch high being preferred.

The bars or blades are preferably disposed to provide coverage aroundthe external surfaces of the body of about 360, although coverage ofbetween about 345 and about 375 is satisfactory. The bars are preferablymade of metal sufiiciently soft topermit milling thereof,

such as during washover operations, this metal preferably being softerthan the metal of the tubular body. For example, the tubular body may bemade of heat-treated hard steel, as is common in the art, and the barsor blades may be made of mild steel. In addition, the external surfacesof the bars radially of the body are preferably hardfaced by suitabletechniques, such as by hardfacing with alloys of suflicient hardness ortungsten carbide. A preferred embodiment in accordance with theinvention also includes hardfacing on the end surfaces of the bars whichlead during entry into the well bore, this hardfacing preferably beingharder than the softer metal in the bars.

The bars are preferably disposed in a helical direction which uponrotation of the stabilizer during entry thereof in a well bore issimilar to that of a right-hand screw. This provides a pumping actionand helps force drilling fluid up between the bars to maintain a clearpassage therethrough and prevent collection of muds and the like. Arighthand helix can also act as a reamer, thereby helping to maintainhole gauge. The bars should be wide enough to provide sufficient lateralbearing surface but thin enough to permit sufiicient passage of drillingfluid thereby.

Preferably, three bars or blades are spaced around the external surfaceof the body symmetrically with the external surfaces of the barsradially of the body each covering in a direction peripheral of the bodyabout thereof, thus providing 360 coverage over the external surface ofthe tubular body.

Another embodiment of the invention comprises a tubular body, means ateach end of the body permitting connection of the drill string, threesubstantially helical bars mounted around the external surface of thebody, and a hard metal ridge substantially longitudinally disposed onthe external surface of the body between each adjacent pair of bars froma point below the ends of the bars which trail during entry into a wellbore to a point above the ends for a distance sufficient to minimizecircumferential erosion of the body by drilling fluid, the tubular bodyhaving an outside diameter, at least under the bars in the ridge,sufficiently less than the outside diameter of an adjacent pipe joint,to the lower end of which the stabilizer is to be connected, to permitmilling of the bars during washover operation without materialinterference from the ridge. The tubular body may have an outsidediameter along its entire length smaller than the outside diameter ofthe adjacent pipe joint, or it may 'be made sufficiently smaller onlyunder the bars and the ridge to permit convenient milling.

The bars or blades are preferably welded on the tubular body inaccordance With conventionally known techniques although the bars may bemounted in grooves or slots and then bolted or otherwise held on.Welding, however, provides a more permanent bonding and consequentlyminimizes breakage of the stabilizer and resultant loss of metal partsin the hole.

In the drawing:

FIG. 1 is an elevational view of an embodiment of a stabilizer inaccordance with the invention;

FIG. 2 is a top plan view taken along the line 2-2 in FIG. 1; and

FIG. 3 is a schematic perspective view of the stabilizer shown in FIG. 1in place in a drill string.

With reference. to FIG. 1 and FIG. 2 in the drawing, the stabilizerthere shown comprises a'tubular body 10 having a threaded projection 12at one end and a threaded socket 14 at the, other end, the projection 12and the socket 14 being of a size suitable for connection in a drillstring, particularly for connection in a string of drill collars orbetween a drill collar and a drill bit. Three bars 16, 18,-and 20 arewelded on the outside surface of the tubular body 10 and aresubstantially helical in shape with a helical direction similar to thatof a righ hand' screw when the stabilizer is entering awell bore.

The bottom ends of the bars 16, 18, and 20 (bottom end 22 of bar 16being the only one shown) and the external surfaces of the bars radiallyof the tubular body 10, that is, the extreme outside bearing surfaces,are hardfaced to provide durability. The other exposed surfaces of thebars 16, 18, and 20 are not hardfaced in order to permit a milling toolto mill the bars away if a washover operation is necessary.

Hard metal ridges 24, 26, and 28 are disposed on the outside of thetubular body 10, each being located between an adjacent pair of barsnear the trailing ends of the bars. As shown, the ridges 24, 26, and 28extend from a point below the trailing ends to a point above thetrailing ends for a distance sufiicient to minimize circumferentialerosion around the tubular body 10 sufliciently as drilling fiuid passesup the outside of the tubular body 10 between the bars.

Ridges 24, 26, and 28 may be made by welding a ridge of sufficientlyhard material on the tubular body 10. The bars 16, 18, and 20 may bemade from rectangular bar stock rolled into a substantially helicalshape, cut to length, and then 'welded on the tubular body 10 in theproper places. The bar stock is preferably rolled to form 24 as well asthe other ridges thereon, and mill away the bars 16,18, and 20 (bar 20not being shown) without the necessity of milling the ridges and withoutmaterial interference from the ridges. The reduced diameter alsoeliminates the necessity of milling the welds holdings the bars on thetubular body. Usually, a reduction in diameter of between about A; to.about 1%: inch or more will be satisfactory.

The combination of hardened ridges to minimize circumferential erosionaround the body 10 and a decrease in the diameter of the body 10 toavoid interference of the ridges during a milling operation provides astabilizer havingiunproved characteristics while avoiding theintroduction of characteristics undesirable .during a milling operation.If a stabilizer in accordance with the inventionis made sufiicientlyshort, for example, below about feet for most commercial operations, andof relatively inexpensive materials, it possesses the desirablecharacteristic of being economically disposable after the bars or bladeswear out, thereby eliminating inconvenient repair at a well site.Suitable'materials of construction will be apparent to those persons inthe art, which materials of course must be selected in view ofconditions expected during a particular use,

What is claimed is:

1. A stabilizer suitable for connection in a drill string, saidstabilizer comprising a tubular body; means at each end of said body forpermitting connection in a drill string; at least to substantially'helical bars fixed mounted on and circumferentially spaced around theexternal surface of said body; and at least one ridge substantiallylongitudinally disposed on said external surface of said body betweeneach adjacent pair of said bars near the ends of said bars which trailduring entry into a well bore.

2. The stabilizer defined in claim 1 wherein said ridge is made of hardmetal and extends longitudinally of said body from a point below thetrailing ends of said bars to a point above the trailing ends of saidbars for a distance suflicient to'minimize circumferential erosion ofsaid body by drilling fluid.

3. The stabilizer defined in claim 1 wherein the external surfaces ofsaid bars provide coverage of about 360 around the external surface ofsaid body.

4. The stabilizer defined in claim 1 wherein each of said bars is madeof metal sufficiently soft to permit milling thereof with the externalsurface of each of said bars radially of said body and the end surfaceof each of said bars at the end which leads during entry into a wellbore being harder than said metal.

5. The stabilizer defined in claim 1 wherein said body is made of metal,and each of said bars is made of a metal softer than the metal of saidbody to permit milling, with only the external surface of each of saidbars radially of said body and the end surface of each of said bars atthe end which leads during entry into a well bore being hardened to beharder than the softer metal of said bars.

6. The stabilizer defined in claim 1 wherein said substantially helicalbars are disposed in a helical direction which upon rotation of saidstabilizer during entry thereof in a well bore is similar to that of aright-hand screw.

7. A stabilizer suitable for connection in a drill string during rotarydrilling; said stabilizer comprising a tubular body; means at each endof said body for permitting connection in a drill string; threesubstantially helical bars fixedly mounted on and symmetrically andcircumferentially spaced around the external surface of said body, eachof said bars having an external surface radially of said body coveringin a direction peripheral of said body about of the periphery of saidbody, said bars being formed of metal sufiiciently soft to permitmilling thereof with only the external surfaces of said bar radially ofsaid body and the end surfaces of said bars at the ends which leadduring entry into a well bore being hardened to be harder than saidmetal; and a ridge disposed substantially longitudinally on said body between each adjacent pair of said bars near the ends of said bars whichtrail during entry into a well bore.

8. The stabilizer defined in claim 7 wherein said ridge is made of hardmetal and extends longitudinally of said body from a point below thetrailing ends of said bars to a point above the trailing ends of saidbars for a distance sufficient to minimize circumferential erosion ofsaid body by drilling fluid.

9. The stabilizer defined in claim 7 wherein said substantially helicalbars are disposed in a helical direction which upon rotation of saidstabilizer during entry thereof in a well bore is similar to that of aright-hand screw.

10. A stabilizer for connection in a drill string, said stabilizercomprising a tubular body; means at each end of said body for permittingconnection in a drill string; three substantially helical bars fixedlymounted on and circumferentially spaced around the external surface ofsaid body; and a hard metal ridge substantially longitudinally disposedon said external surface of said body between each adjacent pair of saidbars from a point below the ends of said bars which trail during entryinto a well bore to a point above these ends for a distance suificientto minimize circumferential erosion of said body by drilling fluid; saidtubular body having an outside diameter, at least under said bars andsaid ridge, sufficiently less than the outside diameter of a pipe joint,to the lower end of which said stabilizer is to be connected, to permitmilling of said bars without material interference from said ridge.

11. The stabilizer defined in claim 10 wherein said bars are made of ametal softer than said body and have hardfacing on only the externalsurfaces of said bars radially of said body.

12. The stabilizer defined in claim 10 wherein said bars are made of ametal softer than said body and have hardfacing on only the externalsurfaces of said bars radially of said body and the ends of said barswhich lead during entry into a well bore.

References Cited by the Examiner CHARLES E. OCONNELL, Primary Examiner.

JAMES A. LEPPINK, Examiner.

1. A STABILIZER SUITABLE FOR CONNECTION IN A DRILL STRING, SAIDSTABILIZER COMPRISING A TUBULAR BODY; MEANS AT EACH END OF SAID BODY FORPERMITTING CONNECTION IN A DRILL STRING; AT LEAST TO SUBSTANTIALLYHELICAL BARS FIXED MOUNTED ON AND CIRCUMFERENTIALLY SPACED AROUND THEEXTERNAL SURFACE OF SAID BODY; AND AT LEAST ONE RIDGE SUBSTANTIALLYLONGITUDINALLY DISPOSED ON SAID EXTERNAL SURFACE OF SAID BODY BETWEENEACH ADJACENT PAIR OF SAID BARS NEAR THE ENDS OF SAID BARS WHICH TRAILDURING ENTRY INTO A WELL BORE.